Program Summary Stroke is the leading cause of adult disability. As the population ages, the incidence of stroke is increasing. Improvements in acute stroke care mean that the death rate from stroke is declining. Stroke has thus changed into a disease of chronically disabled survivors. There is no medical therapy that promotes recovery in stroke. This proposal develops a stem cell therapy for a common subtype of stroke, subcortical or ?white matter? stroke. White matter stroke occurs in the regions of the brain that carry connections, is the most age-associated in its incidence, and is the second leading cause of dementia (termed vascular dementia). The proposed studies characterize the molecular and cellular process in tissue integration and wound healing of an hiPSC-derived cell in brain repair after white matter stroke. This cell is differentiated from an induced human pluripotent cell (hiPSC cell) into an immature glial cell, and is termed an hiPSC-glia enriched progenitor (hiPSC-GEP). Preliminary studies indicate that transplantation of hiPSC-GEPs into a mouse model of white matter stroke enhances behavioral recovery compared to other hiPSC types, and that this behavioral recovery effect is associated with improvement in the MRI appearance of white matter stroke. The studies in this grant will fully determine the phenotype and tissue integration of hiPS-GEPs, the transcriptional profile of hiPSC-GEPs and the cells of the surrounding stroke environment as these two populations re-organize and inter-relate over time after stroke, the effect of hiPSC-GEPs on stroke using in vivo MRI to track tissue repair, and the efficacy of hiPSC-GEPs in translationally relevant stroke conditions, such as in the aging brain. These studies use an innovative platform that includes a new mouse model, in vivo MRI, Drop-seq single cell transcriptional profiling, and viral reporter and gain and loss of function approaches. The proposed studies bring together a neuroscientist/neurologist and stem cell biologist to develop a novel therapy in a disease with increasing prevalence and no current therapy.